| Message ID | 20220823072717.1706-2-tiwai@suse.de |
|---|---|
| State | Accepted |
| Commit | 3e7e04b747adea36f349715d9f0998eeebf15d72 |
| Headers | show |
| Series | [1/2] ALSA: seq: oss: Fix data-race for max_midi_devs access | expand |
On Tue, 23 Aug 2022 09:27:17 +0200, Takashi Iwai wrote: > > It's been reported that there is a possible data-race accessing to the > global card_requested[] array at ALSA sequencer core, which is used > for determining whether to call request_module() for the card or not. > This data race itself is almost harmless, as it might end up with one > extra request_module() call for the already loaded module at most. > But it's still better to fix. > > This patch addresses the possible data race of card_requested[] and > client_requested[] arrays by replacing them with bitmask. > It's an atomic operation and can work without locks. > > Reported-by: Abhishek Shah <abhishek.shah@columbia.edu> > Cc: <stable@vger.kernel.org> > Link: https://lore.kernel.org/r/CAEHB24_ay6YzARpA1zgCsE7=H9CSJJzux618E=Ka4h0YdKn=qA@mail.gmail.com > Signed-off-by: Takashi Iwai <tiwai@suse.de> Gah, there was an obvious type in the patch. The correct version is below, and I merged it now. thanks, Takashi -- 8< -- From: Takashi Iwai <tiwai@suse.de> Subject: [PATCH v2] ALSA: seq: Fix data-race at module auto-loading It's been reported that there is a possible data-race accessing to the global card_requested[] array at ALSA sequencer core, which is used for determining whether to call request_module() for the card or not. This data race itself is almost harmless, as it might end up with one extra request_module() call for the already loaded module at most. But it's still better to fix. This patch addresses the possible data race of card_requested[] and client_requested[] arrays by replacing them with bitmask. It's an atomic operation and can work without locks. Reported-by: Abhishek Shah <abhishek.shah@columbia.edu> Cc: <stable@vger.kernel.org> Link: https://lore.kernel.org/r/CAEHB24_ay6YzARpA1zgCsE7=H9CSJJzux618E=Ka4h0YdKn=qA@mail.gmail.com Link: https://lore.kernel.org/r/20220823072717.1706-2-tiwai@suse.de Signed-off-by: Takashi Iwai <tiwai@suse.de> --- v1->v2: fix compile error sound/core/seq/seq_clientmgr.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c index 2e9d695d336c..2d707afa1ef1 100644 --- a/sound/core/seq/seq_clientmgr.c +++ b/sound/core/seq/seq_clientmgr.c @@ -121,13 +121,13 @@ struct snd_seq_client *snd_seq_client_use_ptr(int clientid) spin_unlock_irqrestore(&clients_lock, flags); #ifdef CONFIG_MODULES if (!in_interrupt()) { - static char client_requested[SNDRV_SEQ_GLOBAL_CLIENTS]; - static char card_requested[SNDRV_CARDS]; + static DECLARE_BITMAP(client_requested, SNDRV_SEQ_GLOBAL_CLIENTS); + static DECLARE_BITMAP(card_requested, SNDRV_CARDS); + if (clientid < SNDRV_SEQ_GLOBAL_CLIENTS) { int idx; - if (!client_requested[clientid]) { - client_requested[clientid] = 1; + if (!test_and_set_bit(clientid, client_requested)) { for (idx = 0; idx < 15; idx++) { if (seq_client_load[idx] < 0) break; @@ -142,10 +142,8 @@ struct snd_seq_client *snd_seq_client_use_ptr(int clientid) int card = (clientid - SNDRV_SEQ_GLOBAL_CLIENTS) / SNDRV_SEQ_CLIENTS_PER_CARD; if (card < snd_ecards_limit) { - if (! card_requested[card]) { - card_requested[card] = 1; + if (!test_and_set_bit(card, card_requested)) snd_request_card(card); - } snd_seq_device_load_drivers(); } }
Apologies, I just realized the previous patch raised incompatible integer conversion warnings on that line during compilation. In the future I'll keep a closer eye out for relevant warnings when testing. This patch still eliminates the race we initially reported. Best, Gabe On Wed, Aug 24, 2022 at 2:03 AM Takashi Iwai <tiwai@suse.de> wrote: > > On Tue, 23 Aug 2022 09:27:17 +0200, > Takashi Iwai wrote: > > > > It's been reported that there is a possible data-race accessing to the > > global card_requested[] array at ALSA sequencer core, which is used > > for determining whether to call request_module() for the card or not. > > This data race itself is almost harmless, as it might end up with one > > extra request_module() call for the already loaded module at most. > > But it's still better to fix. > > > > This patch addresses the possible data race of card_requested[] and > > client_requested[] arrays by replacing them with bitmask. > > It's an atomic operation and can work without locks. > > > > Reported-by: Abhishek Shah <abhishek.shah@columbia.edu> > > Cc: <stable@vger.kernel.org> > > Link: https://urldefense.proofpoint.com/v2/url?u=https-3A__lore.kernel.org_r_CAEHB24-5Fay6YzARpA1zgCsE7-3DH9CSJJzux618E-3DKa4h0YdKn-3DqA-40mail.gmail.com&d=DwIBAg&c=009klHSCxuh5AI1vNQzSO0KGjl4nbi2Q0M1QLJX9BeE&r=EyAJYRJu01oaAhhVVY3o8zKgZvacDAXd_PNRtaqACCo&m=5zfWpItqvL3lHhUMgi-DyAe7DauvBjWwe5UaP0CquJh8c8-phq2TFeGOm0TUvrBw&s=lnBmR8icRLp1uw0Gei6AgrBAaoROKuS3p0LfDWHyyD4&e= > > Signed-off-by: Takashi Iwai <tiwai@suse.de> > > Gah, there was an obvious type in the patch. > The correct version is below, and I merged it now. > > > thanks, > > Takashi > > -- 8< -- > From: Takashi Iwai <tiwai@suse.de> > Subject: [PATCH v2] ALSA: seq: Fix data-race at module auto-loading > > It's been reported that there is a possible data-race accessing to the > global card_requested[] array at ALSA sequencer core, which is used > for determining whether to call request_module() for the card or not. > This data race itself is almost harmless, as it might end up with one > extra request_module() call for the already loaded module at most. > But it's still better to fix. > > This patch addresses the possible data race of card_requested[] and > client_requested[] arrays by replacing them with bitmask. > It's an atomic operation and can work without locks. > > Reported-by: Abhishek Shah <abhishek.shah@columbia.edu> > Cc: <stable@vger.kernel.org> > Link: https://urldefense.proofpoint.com/v2/url?u=https-3A__lore.kernel.org_r_CAEHB24-5Fay6YzARpA1zgCsE7-3DH9CSJJzux618E-3DKa4h0YdKn-3DqA-40mail.gmail.com&d=DwIBAg&c=009klHSCxuh5AI1vNQzSO0KGjl4nbi2Q0M1QLJX9BeE&r=EyAJYRJu01oaAhhVVY3o8zKgZvacDAXd_PNRtaqACCo&m=5zfWpItqvL3lHhUMgi-DyAe7DauvBjWwe5UaP0CquJh8c8-phq2TFeGOm0TUvrBw&s=lnBmR8icRLp1uw0Gei6AgrBAaoROKuS3p0LfDWHyyD4&e= > Link: https://urldefense.proofpoint.com/v2/url?u=https-3A__lore.kernel.org_r_20220823072717.1706-2D2-2Dtiwai-40suse.de&d=DwIBAg&c=009klHSCxuh5AI1vNQzSO0KGjl4nbi2Q0M1QLJX9BeE&r=EyAJYRJu01oaAhhVVY3o8zKgZvacDAXd_PNRtaqACCo&m=5zfWpItqvL3lHhUMgi-DyAe7DauvBjWwe5UaP0CquJh8c8-phq2TFeGOm0TUvrBw&s=Fye5MLoxP4koy4AoFB2JfMaHXzfH8QflMxB0mZrmXOs&e= > Signed-off-by: Takashi Iwai <tiwai@suse.de> > --- > v1->v2: fix compile error > > sound/core/seq/seq_clientmgr.c | 12 +++++------- > 1 file changed, 5 insertions(+), 7 deletions(-) > > diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c > index 2e9d695d336c..2d707afa1ef1 100644 > --- a/sound/core/seq/seq_clientmgr.c > +++ b/sound/core/seq/seq_clientmgr.c > @@ -121,13 +121,13 @@ struct snd_seq_client *snd_seq_client_use_ptr(int clientid) > spin_unlock_irqrestore(&clients_lock, flags); > #ifdef CONFIG_MODULES > if (!in_interrupt()) { > - static char client_requested[SNDRV_SEQ_GLOBAL_CLIENTS]; > - static char card_requested[SNDRV_CARDS]; > + static DECLARE_BITMAP(client_requested, SNDRV_SEQ_GLOBAL_CLIENTS); > + static DECLARE_BITMAP(card_requested, SNDRV_CARDS); > + > if (clientid < SNDRV_SEQ_GLOBAL_CLIENTS) { > int idx; > > - if (!client_requested[clientid]) { > - client_requested[clientid] = 1; > + if (!test_and_set_bit(clientid, client_requested)) { > for (idx = 0; idx < 15; idx++) { > if (seq_client_load[idx] < 0) > break; > @@ -142,10 +142,8 @@ struct snd_seq_client *snd_seq_client_use_ptr(int clientid) > int card = (clientid - SNDRV_SEQ_GLOBAL_CLIENTS) / > SNDRV_SEQ_CLIENTS_PER_CARD; > if (card < snd_ecards_limit) { > - if (! card_requested[card]) { > - card_requested[card] = 1; > + if (!test_and_set_bit(card, card_requested)) > snd_request_card(card); > - } > snd_seq_device_load_drivers(); > } > } > -- > 2.35.3 >
diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c index 2e9d695d336c..052a690b5e11 100644 --- a/sound/core/seq/seq_clientmgr.c +++ b/sound/core/seq/seq_clientmgr.c @@ -121,13 +121,13 @@ struct snd_seq_client *snd_seq_client_use_ptr(int clientid) spin_unlock_irqrestore(&clients_lock, flags); #ifdef CONFIG_MODULES if (!in_interrupt()) { - static char client_requested[SNDRV_SEQ_GLOBAL_CLIENTS]; - static char card_requested[SNDRV_CARDS]; + static DECLARE_BITMAP(client_requested, SNDRV_SEQ_GLOBAL_CLIENTS); + static DECLARE_BITMAP(card_requested, SNDRV_CARDS); + if (clientid < SNDRV_SEQ_GLOBAL_CLIENTS) { int idx; - if (!client_requested[clientid]) { - client_requested[clientid] = 1; + if (!test_and_set_bit(clientid, client_requested)) { for (idx = 0; idx < 15; idx++) { if (seq_client_load[idx] < 0) break; @@ -142,10 +142,8 @@ struct snd_seq_client *snd_seq_client_use_ptr(int clientid) int card = (clientid - SNDRV_SEQ_GLOBAL_CLIENTS) / SNDRV_SEQ_CLIENTS_PER_CARD; if (card < snd_ecards_limit) { - if (! card_requested[card]) { - card_requested[card] = 1; + if (!test_and_set_bit(card_requested, card)) snd_request_card(card); - } snd_seq_device_load_drivers(); } }
It's been reported that there is a possible data-race accessing to the global card_requested[] array at ALSA sequencer core, which is used for determining whether to call request_module() for the card or not. This data race itself is almost harmless, as it might end up with one extra request_module() call for the already loaded module at most. But it's still better to fix. This patch addresses the possible data race of card_requested[] and client_requested[] arrays by replacing them with bitmask. It's an atomic operation and can work without locks. Reported-by: Abhishek Shah <abhishek.shah@columbia.edu> Cc: <stable@vger.kernel.org> Link: https://lore.kernel.org/r/CAEHB24_ay6YzARpA1zgCsE7=H9CSJJzux618E=Ka4h0YdKn=qA@mail.gmail.com Signed-off-by: Takashi Iwai <tiwai@suse.de> --- sound/core/seq/seq_clientmgr.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-)